As a child growing up in the 1970's, one of my favourite things was my GAF Viewmaster.
The GAF Viewmaster is a hand-held contraption used to view seven 3-D images, or stereo images that are mounted on a small disc. The way it works is that you look at 14 film slides that are paired through a sort of binocular like device that focuses the paired photographic slides into stereoscopic images. These days, Viewmasters are aimed more at children, but their original targeted market back in the 1940's/1950's, was considerably more adult-orientated with a heavy emphasis on education and tourism, something demonstrated by the titles on offer which included spectacular images of cities, tourist hotspots and wildlife from around the world, as well as national/general interest/reportage events such as Trooping The Colour in the U.K., the wedding of Prince Rainier III and the actress Grace Kelly or the Coronation of Queen Elizabeth II.
The early 1950's saw the beginning of the more child-friendly images when deals were done with Disney, the Viewmaster, then owned by Sawyer, started to produce discs with images of Disney characters and then images of Disneyland when it opened in 1955.
It was in 1966 that the General Aniline and Film (GAF) Corporation bought Sawyers, and Viewmaster became owned completely as a subsidiary. GAF focused on fewer scenic discs and produce more discs aimed at children with subjects such as toys and cartoons as well as television series such as Star Trem, U.F.O., Doctor Who, The Man From Uncle and Flipper.
My own Viewmaster is a beige Model G from the 1960's and is in very good shape for it's year. I have a few discs, most from the mid-20th Century including "The Norfolk Broads", "London", "Star trek: The Omega Glory" and "Niagra Falls", but have now decided to start collecting seriously. There are hundreds of titles and thankfully, there is a quite a following for these lovely little relics of a childhoods past meaning that they are, by and large, readily available.